Thallium complexes iodides

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

Mercuration of aromatic compounds can be accomplished with mercuric salts, most often Hg(OAc)2 ° to give ArHgOAc. This is ordinary electrophilic aromatic substitution and takes place by the arenium ion mechanism (p. 675). ° Aromatic compounds can also be converted to arylthallium bis(trifluoroacetates), ArTl(OOCCF3)2, by treatment with thallium(III) trifluoroacetate in trifluoroace-tic acid. ° These arylthallium compounds can be converted to phenols, aryl iodides or fluorides (12-28), aryl cyanides (12-31), aryl nitro compounds, or aryl esters (12-30). The mechanism of thallation appears to be complex, with electrophilic and electron-transfer mechanisms both taking place. 

Contrary to In3+, the heaviest d acceptor of group 3B, Tl +, is a very soft acceptor, as is evident from the stabilities of its chloride and bromide complexes (Table 2). The lower iodide complexes are not stable relative to the redox reaction producing thallium(I) and free iodine. The inherent affinity of T13+ for 1 is so strong, however, that even at rather modest concentrations of free iodide, thallium (III) is completely protected from reduction by formation of the complex Tlli (80). The value... 

Access to the 1,3-benzazepinone 39 has been achieved from aryl iodide 38 with a Pd(0) catalyst, followed by cyclization of the intermediate palladium complex upon reaction with thallium acetate, thus providing a convenient approach to the fused seven-membered ring system (Equation 5) <1998ICA(270)123>. 

Chromium carbene complexes. phloroglucinols Malonyl dichloride. phthalides Thallium(III) trifluoroacetate. pinacols Samarium(II) iodide. Tetra-w-butylammonium fluoride. 

Fluoride, chloride, bromide, and iodide derivatives of thallium(I) are well known. Their solubilities and photosensitivity are similar to the corresponding silver(I) systems. TIE is water-soluble, whereas the chlorides, bromides, and iodides are water-insoluble solids. This property is exploited in ligand-transfer chemistry involving thallium precursors. Some solid-state structures of thal-lium(I) salts of weakly coordinated anions show TT -halide interactions. Selective abstraction of a fluoride from a C-F bond, leading to thallium fluoride, has been described. The compound [ P(CH2CH2PPh2)3 RuH( 7 -ClTl)]PF6 represents the first metal complex containing an 77 -Cl-bonded TlCl ligand. This compound act as a thallium(I)-ion carrier. 

Thallium(I) chloride, bromide and iodide are made by precipitation from a thallium(I) sulphate solution. TlCl resembles AgCl in solubility, structure and sensitivity to light but is insoluble in ammonia the T1+ ion is evidently too large to form ammonia complexes. TIF is yellow and resembles AgF in colour, structure and solubility. 

Antimony can be separated from bismuth by extraction into benzene from iodide medium. From 5 M H2SO4 and 0.05 M KI solution, Sbli is extracted in a good yield, whereas the bismuth complex is not extracted at all. Thallium is precipitated as T1(I) and separated by filtration [36]. Copper is masked with thiourea. 

In a hydrochloric acid medium (optimum concentration -0.5 M HCl), thallium(I) is oxidized with bromine to thallium(III). Thallium(III) oxidizes iodide to iodine, which gives a blue complex with starch. The molar absorptivity of the starch-iodine complex is 3.9-10 (a = 0.19) at 590 nm. 

Some other organic reagents for determining thallium include Bromopyrogallol Red [52-54] (in the presence of CP, e = 3.610 ) [52]. Thallium(III) has been determined as the yellow iodide complex [2,55], which may be extracted into benzene in the presence of DAM or DAPM (e = 1.2-10 at 400 nm). The thiocyanate complex of Tl(III) in the presence of pyridine has also been used for determining thallium [56]. 

These spectral features and other evidence presented in this paper (97) leave no doubt that the Tl(III) cyano complexes exist, that they have the stated composition, and that they are extremely strong and kinetically inert. In fact, the cyano complexes are stronger than any other known monodentate complexes of thallium(III). The only possible known competitor as a ligand, the iodide ion, forms the complex TII4 with the overall stability constant log = 35.7 (99), i.e., several orders of magnitude lower than that of T1(CN)4" (see Table III). The distribution of thallium among the various Tl(CN), "-species is shown in Fig. 5. Stepwise stability constants of MX complexes often decrease with increasing n because of statistical, steric, and coulombic factors... 

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